TX 200 Breech seal

[Vernal]

Not really on topic, but as there are some very knowledgeable people following this thread, I wonder if someone could tell me the standard transfer port diameter for a TX? I have checked mine at 3.6 mm, and wonder if this is as original

[Shed tuner]

Not really on topic, but as there are some very knowledgeable people following this thread, I wonder if someone could tell me the standard transfer port diameter for a TX? I have checked mine at 3.6 mm, and wonder if this is as original

3.7mm std, so sounds like yours is normal. If anything it's on the large side - 3.2-3.4 is better

[Phil Russell]

3.7mm std, so sounds like yours is normal. If anything it's on the large side - 3.2-3.4 is better

Once again, excellent info for the 'very useful to know file'.
I had begun to search for TP info and found reference to the TX200 MK3 having a port of around 3.7 - 3.8 with the MK1 and 2 having the narrower port of 3.2.
Can this be confirmed?

Also ... maybe a little off-beat but I was looking at a MK2 compression tube from my spares box that had no BS108 rings fitted and I am sure there is a steel washer or something that would seat under the breech rings. Not sure this is odd or not. Pretty sure I can revolve it using a needle. Or maybe my eyes are playing up. Any ideas?

Cheers, Phil

[Vernal]

Once again, excellent info for the 'very useful to know file'.
I had begun to search for TP info and found reference to the TX200 MK3 having a port of around 3.7 - 3.8 with the MK1 and 2 having the narrower port of 3.2.


Cheers, Phil

I measured mine using drill bits- 3.6 fitted, 3.7 just didn't, so it could well really be 3.7.
It is a Mk.3 tube running a Mk 2 piston - would it be worth looking for a Mk 2 tube?

[Vernal]

I can't think what prompted me to do it, but I just took a look at the inside of the transfer port using a 10X lens. Shock horror, at first I thought someone must have started to cut an internal thread in it, but a closer look shows that the row of grooves about 0.1 - 0.2 mm deep are not helical, but in series going most of the way down the port (I wish I could photograph this). Another check found that the 3.7 drill, which will not fit into the entry end (see my earlier post) goes about half way through from the exit end.
I know that a polished surface is not considered a must for the tp, but the turbulence as the air passes over these deep grooves must be immense, so much so that it may be the cause of the gun struggling to make full power?
So what should I do now? I don't have the engineering facilities to sleeve the port and as far as I can see the end plug is not available separately as a spare. Should I try opening the port to 3.8, which should get rid of most of the rings, or do I give up and buy a whole new cylinder? I don't like the idea of just leaving it as it is

[Turnup]

Interesting observation. You observe a slightly tapered TP with circumferential ribbing and that seems unlikely to be accidental to me.

Might be a red herring but I am minded of a certain German aircraft (Junkers sommat or other?) which has a ribbed surface on the fuselage perpendicular to the air flow. Was originally done to increase stiffness but they found, contrary to instinct, it actually reduced parasitic drag by disrupring the laminar air flow. This is a low speed aeroplane and different effects might prevail as the air velocity increases. Also air flows in the confined space of the TP could be entirely different. Are they all like that I wonder?

[Vernal]

Interesting observation. You observe a slightly tapered TP with circumferential ribbing and that seems unlikely to be accidental to me.

Might be a red herring but I am minded of a certain German aircraft (Junkers sommat or other?) which has a ribbed surface on the fuselage perpendicular to the air flow. Was originally done to increase stiffness but they found, contrary to instinct, it actually reduced parasitic drag by disrupring the laminar air flow. This is a low speed aeroplane and different effects might prevail as the air velocity increases. Also air flows in the confined space of the TP could be entirely different. Are they all like that I wonder?

The grooves do not look nearly regular enough to be intentional, they vary significantly in width, depth and separation, and look as if a piece of damaged tooling was used to make the hole - probably whatever Air Arms used to make it in the first place. Can't imagine how it could have got through QC though.